John, As Doug says "it depends" (OK, I owe Mr. Pauls a Mtn Dew) If your final finish does not add chemical entrapment concerns or if you really need one side sealed for vacuum or if you are concerned with solder bleed through during wave or if you are probably starting to see there are multiple factors to consider. I would start with the why do you want to mask 1 side and follow up with a conversation with your fabricator. Some houses will say no worries, while others will shriek with concern. If you use one or two fabricators and they agree, then go ahead, but if you don't have say in who builds your boards (it's a purchasing decision), then you may want to stay on the cautionary side of not masking. ENIG, IAg, ISn and OSP all need to wash through the hole for good coverage and protection of the copper, so if you call out SMOBC there is a real possibility of chemical entrapment. If you allow final finish to be applied prior to soldermask then there should be minimal concerns. Figure out your reasoning why you want it and talk to your supplier to decide if it really makes sense (both in performance and cost). Hope it helps. FNK Frank N Kimmey CID+ Principal PCB Designer PCB Programs Powerwave Technologies Inc Office 916-941-3159 Fax 916-941-3195 Mobile 916-670-0645 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Foster Sent: Tuesday, May 01, 2007 8:48 AM To: [log in to unmask] Subject: [TN] unsymetrically masked vias Is it problematic for a fabricator if a via .062 board 10 mil finished via is masked on one side and not the other? Any input will be appreciated Thank You John Foster --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------